The present invention is directed to an improved device for shredding documents which device has two rotating members having a plurality of knife-like cylindrical members that are interdigitally mounted to shred a document as it passes therebetween.
In order to destroy documents to preserve their confidentiality, it is known to cut the documents in narrow strips in a process which is commonly referred to as shredding. A specific way of shredding is achieved with circular knives or cutters which are arranged along an axis of a rotating member and coact with a second member having similar knives which are offset so that the knives of one member pass between the rotating knives of the other member. In addition, stripping arrangements are positioned between the rotating knives on each of the two rotating members to insure that the shredded material does not stick.
The actual structure of the rotating members having knives or cutters can be a solid bar of steel or similar material in which the knives and cutters are formed by machining so that the cutter and the spacer are all integral to one another. Another structure has separate cylindrical members of a large diameter which are utilized as the knives or cutters and are spaced apart by separate cylindrical spacers which are assembled on a shaft in an alternating relationship. A third structure is a plurality of sleeves having integral knives and spacers, which sleeves are then assembled on shafts to form the rotating members. The shredding device also has strippers or paper guides which are utilized and extend in the area of the spacer for the purpose of guiding the material into the two rotating members or cutting rolls and also to lead the shredded material out on the discharge side as severed or cut strips.
One problem with known and existing shredding devices is that when overloaded by too thick a stack of documents to be shredded, the shafts or rotating members will be bent or flexed so that the document or paper will pass through in one piece and not be shredded into strips. This passing through of the documents in an unshredded condition will cause jamming which will require taking the machine apart for correction. It has been proposed to provide the shredding device with automatic reversing mechanism so that when the rotating members begin to jam and the speed of the motor is reduced, the drive motor will reverse the direction of rotation of the cutting blades to expel the document. An example of such a system is disclosed in copending U.S. patent application No. 422,282 which was filed Sept. 23, 1982. However, this automatic reversing device may malfunction or be overridden by the operator so that a jamming of the documents can still occur.